Combination roughing and finishing hob



RB VICH.

HING HOB.

} Patented June 15, 1920.

have invented the ratio is section is of considerable axial which adjoins To all whom it may concern:

- citizen of the United 'worm wheels used in wormdrives.

may accurately produce a great turret STA Ann G. onson AND NIKOLA rrtnozrnvrcn, or cnrcneo,

ILLINOIS,-A conronnrron or innmors.

, ILLINOIS TOOL WORKS, OF'OHIGAGO,

COMBINATION ROUGHING AND FINISHING HOB.

Application filed August 9,

Be it known that we,- CARL G. OLSON, a- States of America, and NIKOLA TRBOJEVIGH, a subject of the King of Jugo-Slavia, both residing at Chicago, in the county of Cook and State of Illinois,

a certain new and mprovement 1n Combination Roughing and Finishing Hobs, of which thefollowmg 1s a ecification.

ur invention relates to hobs, and s particularly. adapted for the production of It is of especial value in'worm drives of a ratio approximating unity-that is, where the speed ratio is somewhere near one v The general object of the invention 1s to produce a hobcapable of advantageously roducing a' worm gear of this type.- contributory object is to provide a hob which number of character in which anywhere near one to one rcuires that the gear shall be accurately ormed, and consequently, the hob which produces it must maintain its accuracy. In order to obtain the best results, the diameter gears. .A drive of this of the-hob should be approximately equal to the diameter of theworm gear, and

one ob'ects of our invention is to produce hich will maintain its proper diameter over a long period of time, thus promoting economy as well as accurac In carrying out our invention, we have produced a hob formed'in two separable sections. One of these constitutes the roughing section and the other the finishing section. In the design shown, the'roughing length, while the finishing section is practically a ringthat is, the axial length is comparatively short. In the roughin section the teeth are smaller than in the nishing section, and furthermore, the roughing section, when viewed in outline, is tapered, the forward end being of smaller diameter than the end the finishing section. This appearance is due to the fact that at the forward end of the roughing section the teeth are not so high as at the rear end, although the root circle remains constant from one end of the roughing section to the other.

Specification of Letters Patent. Patented Fig.2 shows-the parts height of the teeth. Thus the teeth'are res; PATENT oF'F'ic.

rumors, nssreuons To 1919. sem K035165361.

' r We accomplish our objects by the construction illustrated in the accompanying drawings, in'whi'ch- Figure 1 is an assembly compound hob mounted upon an arbor. In association with the-hob there is shownin dotted lines the'position of the work before itreaches the hob, and in full lines the posi- June 15, 192 0.

tion and appearance of .thework afterit has been fed past the hob.

v f the hob separated on the arbor. 4 I

- Fig. 3 shows the type of worm gear which our hob is adapted-to produce. This is some- .times known as the worm gear having an Hindley gear or a hour glass shape. Like numerals denote like out the several views.

In the form shown in thedrawi-ngs, the hob consists of arouggling -section 1 and a finishing section 2. he roughing section is somewhat smaller in diameter and. the teeth thinner than in the finishing section. It is of considerable length axially, .and while this dimension may be varied, it is desirable that the lengthhall be not much less than one-half of the diameter and it may be somewhat more if desired. I he teeth of the roughing those'at the forward at the rear end-that To accomplish this the parts through.-

section are tapered so that end are thinner than end adjoining.

producing lathe is geared up so as to ad-. vance the producing tool on one side somewhat less than the basic helical lead of the thread of the hob, and on the other sidesomewhat more than the basic helical lead of the thread, of the hob, The included difference in the length of a hob of this variafrom 1/64 to 1/32 of an inch, and this will make the front teeth correspondingly thinner than the rear teeth. The hob is also relieved in such manner that the hei ht of the teeth at the forward end is less t an at i shorter and thinner at the forward end of the hob and gradually increase in thickness both tion in lead mayamount to approximately view showing our lot diameter is. constant, the H and height toward the rear end. At the rear end they are practically if not quite full size and hei ht.

,Thefinishmg section 2, in the preferred form, has simply a single row of teeth dis-- tributed circumferentially, the forward or cutting end being of full outline so as to i to rigidly maintain their proper axial ment.

produce a worm gear of accurate configuration. The individual teeth of thefinishing section are, however, relieved as in an ordinar hob.

'l he roughing section has a hub 5 on its larger or rear end which fits into a counter bore or socket 6 formed in the forward end or face of the finishing sectlon. By thus causing the parts to interfit they areenalbled a me- While the manner of mounting the .sections of the hob may be varied somewhat an advantageous construction is illustrated in the drawings. In'this form an arbor is employed, the portion 7 being of full diameter with a portion 8 of reduced diameter adjacent to it whereby an annular shoulder 9 is formed. The hob sections 1 and 2 fit slid ingly over the portion 8 and so also does a spacing sleeve. 10. A portion 12 of thearbor is still further reduced in diameter, this portion being threaded to take a lock nut When the parts are assembled as shown in Fig. 1, the hob sections 1 and 2 are held tight together between the shoulder 9- and sleeve 10, and the sleeve is held in positlon by the nut 13. The portion :8 of the arbor is which the provided with a feather 14 b hob sections are splined to the ar or, and thus rigidly held against an lar movement relatively to each other. t is important that the hob sections should be accurately assembled, angularly, so'that the helical sequence of the teeth of the two sections will be maintained. The splining of the parts on the arbor 'accom lishes this, care being required in the manut keyways of the two sections positioned.

In practice, whenthe parts are assembled,

are accurately as-described and as shown in Fig. 1, the parts are rotated and are fed in the manner typified by the arrows in said fi re. Assuming that the roughing hob is p aced toward theleft, and the helical lead of the runs as illus-- trated, the top of the hob will rotate toward the observer and the worm gear to be roduced (indicated by the numeral 15) will rotate in a clockwise direction. The work will be fed toward the right or, if preferred, the hob may be fed toward the left, although the former method is preferred in practice. The hob and the work are rotated in timed relation and after the work has traveled past the hob .it will appear as shown in full line at the right end of Fig. 1. When viewed from the side the finished work will appear spiral worm acture of the hob to see that the.

as shownin Fig. 3. According "to the pro portions illustrated, the work produced will be 1n the form of a Hindley or hour glass gear adapted for a one tcfone speed ratio.

As a result of our invention it becomes possible to produce a worm gear of the type shown in a practical. and commercial mar ner. The roughing hob section, as its name lndicates, roughs out the work, but before leaving-1t brings it to .a state approach pieces of work only alimited number of resharpenings are permissible. But with our construction, the finishing section maybe used a long time without resharpenin and when worn down to the lowest permissible limit a new finishing section may be substituted but the ori inal roughing hob may still be employed, thus enabling the user to get maximum value out of the tool.

we claim as new and desire tosecure by Letters Patent, is I 1. A-compoundhob having a plurality of individual. separable sections, one con- Having thus described our invention what I stituting a roughing section and anothema finishing section, means for holding them in axial alinement, and means for locking th proper positlon angularly about the age of rotation.

2. A hob consisting of a roughing section and a finishing section havin helically arranged teeth, said sections being separable, means for holding said sections side byside in axial alinement, and means for locking said sections relatively rigid with their teeth in proper angular sequence.

3. A hob having helically arranged teeth, said hobhaving a rou hin section and a finishing section, separa 1e rom each other,

an arbor for supporting and rotating saidsections, and means for locking said sections to the arbor with the teeth in proper helical sequence. I v

4. A hob having teeth arranged helically saidhob consisting of a finishing section and a roughing section helically in advance of the finishing section, and separable from it, an arbor adapted to support the sections side by side and rotate them, said sections having interfitting ends for adding to the rigidity with which the sections are held in axial 'alinemen't, and means for locking the 189 sections against relative rotation to thereby ing section having helically configurated 1 insure that the teeth shall be and remain in teeth arranged helicall the roughing teeth proper helical sequence. being smaller. than the finishing teeth and the v 5. A- hob havingla roughing section and a finishing teeth loein helically configurated 5 finishing section, t e finishing section having but arranged in the em of a ring concentric 15 a single row of teeth distributedcircumfenwith the axis of the tool. entlally whereb all of the teeth of the work In witness whereof we have hereunto 'subare fimshed at t e same time. scribed our names. 6. A hob consisting of a roughing section I I 0 RL Gr. OLSON. 10 and a separate finishing section, the rough- 4 NIKOLA TRBOJEVICH. 

